Other Comprehensive Income (Loss) (Schedule of Changes in AOCL by Component) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 5.2
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(5.4)
Other comprehensive income (loss)
Total Other Comprehensive Income (Loss), net of tax	(16.9)	$ 10.3
Accumulated other comprehensive loss
Beginning balance	1,616.2
Net activity	(16.9)	10.3
Ending balance	1,551.5
Available-for-sale Securities and Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.8
Other comprehensive income (loss)
Prior to reclassification	(1.7)	5.8
Reclassification from	(2.2)	(0.4)
Pre-tax	(3.9)	5.4
Tax effect	0.2	(2.0)
Total Other Comprehensive Income (Loss), net of tax	(3.7)	3.4
Accumulated other comprehensive loss
Beginning balance	16.8	4.3
Net activity	(3.7)	3.4
Ending balance	13.9	7.7
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0
Other comprehensive income (loss)
Prior to reclassification	(13.6)	6.1
Reclassification from	0.0	0.0
Pre-tax	(13.6)	6.1
Tax effect	0.0	0.0
Total Other Comprehensive Income (Loss), net of tax	(13.6)	6.1
Accumulated other comprehensive loss
Beginning balance	(105.3)	(81.3)
Net activity	(13.6)	6.1
Ending balance	(118.9)	(75.2)
Change in Pension and Postretirement Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(6.2)
Other comprehensive income (loss)
Prior to reclassification	0.0	(0.1)
Reclassification from	0.5	1.2
Pre-tax	0.5	1.1
Tax effect	(0.1)	(0.3)
Total Other Comprehensive Income (Loss), net of tax	0.4	0.8
Accumulated other comprehensive loss
Beginning balance	(24.5)	(33.0)
Net activity	0.4	0.8
Ending balance	(30.3)	(32.2)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(5.4)
Other comprehensive income (loss)
Prior to reclassification	(15.3)	11.8
Reclassification from	(1.7)	0.8
Pre-tax	(17.0)	12.6
Tax effect	0.1	(2.3)
Total Other Comprehensive Income (Loss), net of tax	(16.9)	10.3
Accumulated other comprehensive loss
Beginning balance	(113.0)	(110.0)
Net activity	(16.9)	10.3
Ending balance	(135.3)	(99.7)
Foreign Exchange Forward [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0
Foreign Exchange Forward [Member] | Available-for-sale Securities and Hedges [Member]
Other comprehensive income (loss)
Prior to reclassification	1.2	(0.9)
Reclassification from	0.1	(0.4)
Pre-tax	1.1	(0.5)
Tax effect	0.4	(0.1)
Total Other Comprehensive Income (Loss), net of tax	0.7	(0.4)
Accumulated other comprehensive loss
Beginning balance	0.2	(0.4)
Net activity	0.7	(0.4)
Ending balance	0.9	(0.8)
Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.8
Interest Rate Swap [Member] | Available-for-sale Securities and Hedges [Member]
Other comprehensive income (loss)
Prior to reclassification	(5.1)	6.7
Reclassification from	2.1	0.8
Pre-tax	(7.2)	5.9
Tax effect	(1.9)	2.1
Total Other Comprehensive Income (Loss), net of tax	(5.3)	3.8
Accumulated other comprehensive loss
Beginning balance	18.3	4.7
Net activity	(5.3)	3.8
Ending balance	13.8	$ 8.5
Currency Swap [Member] | Available-for-sale Securities and Hedges [Member]
Other comprehensive income (loss)
Prior to reclassification	2.2
Reclassification from	0.0
Foreign Exchange Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0
Foreign Exchange Contract [Member] | Available-for-sale Securities and Hedges [Member]
Other comprehensive income (loss)
Pre-tax	2.2
Tax effect	1.3
Total Other Comprehensive Income (Loss), net of tax	0.9
Accumulated other comprehensive loss
Beginning balance	(1.7)
Net activity	0.9
Ending balance	$ (0.8)